1. Field of the Invention
The present invention relates to a semiconductor integrated circuit device including a monitor circuit for performing the characteristic test of semiconductor devices.
2. Description of the Related Art
In the semiconductor integrated circuit device, the characteristics of internal semiconductor devices have been investigated. However, since such a semiconductor device is connected to the other semiconductor devices, wirings and the like in the same circuit, it is added to the impedances thereof, which makes it difficult to independently investigate the objective device from the outside.
Accordingly, the isolated monitor circuit is built-in the semiconductor integrated circuit device, and the characteristic of the monitor circuit is tested. Thus, on the basis of the characteristic of the device thus obtained, the characteristic of the device in the semiconductor integrated circuit is estimated.
The monitor circuit electrically isolated from the semiconductor integrated circuit main body has been provided various semiconductor integrated circuit devices.
FIG. 1 (Prior Art) schematically shows the common relationship between a monitor circuit and a semiconductor integrated circuit main body, wherein a monitor circuit M is formed independently from a semiconductor integrated main body L, and various tests are made through pads P1 to P3 connected to the monitor circuit M.
In the case of testing the characteristic of the device used, however, the monitor circuit M described above is not suitable. The reason for this is as follows:
The change in characteristic of the device inside the semiconductor integrated circuit L used is often affected by the change in voltage or current during operation due to hot carrier, electromigration and the like. As a consequence, even if the characteristic change is investigated by driving the monitor circuit M independently from the semiconductor integrated circuit L, the result is actually different from the characteristic change of the device inside the semiconductor integrated circuit L.
In the case of testing the characteristic of the device used, the objective device is separated from the semiconductor integrated circuit main body L using the technique such as etching, laser cutting or the like, and further, the wirings connected to the device are exposed by etching the preventive film covering the device and the like by etching, thus carrying out the measurement using the above wirings as electrodes for testing.
The measurement for the characteristic of the device according to such processes takes a lot of labor and time, and also often causes the further characteristic change of the device during the operation, and therefore, it becomes difficult to accurately investigate the characteristic change due to the deterioration of the device.